Animal Coordination, Control and Homeostasis Flashcards
What are hormones?
They are ‘chemical messengers’ that target organs in the body
What are hormones produced by?
Endocrine glands and they are released into the blood
What do target organs do in response to its hormone?
Release another chemical susbtance
What are the seven endocrine glands?
Pituitary Thyroid Pancreas Testis Hypothalamus Adrenal Ovary
What is the pituitary gland?
Located at the base of the brain, it releases many hormones including ACTH, FSH, LH and growth hormones.
What is the thyroid gland?
Located at the base of the neck, it secretes thyroxine
What is the pancreas?
Located high in the abdomen, its cells secrete insulin and glucagon
What are the testes?
Located in the scrotum, they secrete the sex hormone testosterone
What is the hypothalamus?
Located in the brain, it produces TRH and CRH
What is the adrenal gland?
Located in each kidney, they secrete adrenalin
What are the ovaries?
Located in the pelvis, they produce the sex hormones oestrogen and progesterone
What is a target organ?
An organ that is affected by a specific hormone
What are the similarities between nerves and hormones?
They both help you respond to changes in the environment and in your body
What are the differences between nerves and hormones?
- Hormones = long-lived effect, take longer to work
- Nerves = short-lived effect, works quickly
When do the release of sex hormones increase?
During puberty, explaining the increase in growth rate at this time
What does thyroxine do?
Controls your metabolic rate (rate of respiration/hunger levels) by causing heart cells to contract more rapidly and strongly and increases rate at which proteins and carbs are broken down into cells
What happens if your produce too much thyroxine?
High metabolism = hyperactive, constant hunger, lose weight fast
What happens if you produce too little thyroxine?
Slow metabolism = depressed, tired, gain weight easily
How is the control of thyroxine concentration in the blood an example of negative feedback?
Sn increase in thyroxine concentration directly causes changes that bring about a decrease in the amount of thyroxine released into the blood
What happens in frightening/exciting situations in association with adrenalin?
An increase in impulses from neurones reaching the adrenal glands from the spinal cord triggers the release of large amounts of adrenalin into the blood
What is glycogen?
A polymer made of glucose molecules
What can happen when glycogen is broken down?
The glucose molecules can be released into the blood providing additional glucose for respiration
What does adrenalin do to the heart?
- Heart muscle cells contract more rapidly, increasing heart rate
- Heart muscle cells contract more strongly, increasing blood pressure
What does adrenalin do to the liver?
Liver cells change glycogen to glucose and release it into the blood, increasing blood sugar concentration
What does adrenalin do the blood vessels?
- Narrow those leading to other organs = reduces blood flow to organs, increasing blood pressure
- Widen those leading to muscles = increases blood flow to muscles
What is the menstrual cycle?
A cycle of changes in a woman’s reproductive system that takes about 28 days
When does the menstrual cycle occur?
From puberty (12) to menopause (50s)
What does the menstrual cycle do?
Prepares the woman’s body for the fertilisation of an egg cell (pregnancy)
What happens during the menstrual cycle?
The lining of the uterus thickens again and ovulation occurs
What is ovulation?
When an egg cell is released from an ovary
What happens on days 1-5 of the MC?
Menstruation begins and the uterus lining breaks down and is lost with the unfertilised egg cell
What happens on day 11 of the MC?
Menstruation ends and the uterus lining starts to thicken again
What happens on days 13-15 of the MC?
Ovulation occurs (ovary releases an egg)
When is fertilisation most likely?
After ovulation (days 16+)
What happens on day 23?
The egg cell travels along the oviduct to the uterus
What is the cycle controlled by?
Sex hormones oestrogen and progesterone
Where are the sex hormones released from?
The ovaries into the blood
What happens during sex?
Sperm cells are deposited in the vagina which pass through the cervix to the uterus and into the oviduct; if a sperm cell meets an egg cell, fertilisation can occur
What is contraception?
The prevention of fertilisation, methods being physical barriers or uses of hormones
Describe the male condom,
- 98% success rate
- Placed over erect penis, preventing sperm entering vagina
Describe the diaphragm/cap
- 92-96% success rate
- Placed over the cervix (entrance to the uterus), preventing sperm in the vagina entering the uterus
Describe the hormone pill and implant under skin
- > 99% success rate
- Releases hormones to prevent ovulation and thickens mucus at the cervix, making it difficult for sperm cells to pass through
What controls the release of FSH and LH?
The concentration of oestrogen and of progesterone
When does the concentration of oestrogen increase?
As the egg follicle matures
When is progesterone released?
After ovulation when the follicle becomes a structure called the corpus luteum
What does hormonal contraception use?
A progesterone-like hormone either on its own or with progesterone
What does raising hormone concentrations in hormonal contraception prevent?
The natural fall of hormone concentrations at the end of the menstrual cycle
How can problems with couples unable to get pregnant be overcome?
Using ART (Assisted Reproductive Technology), which uses hormones and other techniques to increase the chance of pregnancy
What is clomifene therapy?
- It is useful for women who rarely or never release an egg cell during their menstrual cycles
- Clomifene is a drug that helps to increase the concentration of FSH and LH in the blood